To do so, edit the galler.
Click the "advanced" link near the top of the page to edit the advanced gallery settings.
The first setting is "enable voting".
Check the box to have voting enabled. Uncheck to box to have voting disabled.
Click the "Update Advanced Settings" button.

You can enable or disable voting on your galleries.
To do so, edit the galler.
Click the "advanced" link near the top of the page to edit the advanced gallery settings.
The first setting is "enable voting".
Check the box to have voting enabled. Uncheck to box to have voting disabled.
Click the "Update Advanced Settings" button.

When viewing a gallery, you have the option to "vote for this gallery". When a gallery receives at least one vote, it will appear in the Popular Galleries. Voting for an image, however, will not put the gallery in the Popular Galleries. When viewing a particular image, you have the option to "vote for this image". When an image receives a vote, just that image will appear in the Popular Photos section, rather than that entire gallery appearing in the popular galleries.